Dark matter particle spectroscopy at the LHC: generalizing MT2 to asymmetric event topologies

We consider SUSY-like missing energy events at hadron colliders and critically examine the common assumption that the missing energy is the result of two identical missing particles. In order to experimentally test this hypothesis, we generalize the subsystem M-T2 variable to the case of asymmetric event topologies, where the two SUSY decay chains terminate in different "children" particles. In this more general approach, the endpoint M-T2(max) of the M-T2 distribution now gives the mass (M) over tildep((M) over tilde ((a))(c),(M) over tilde ((b))(c)) of the parent particles as a function of two input children masses (M) over tilde ((a))(c) and (M) over tilde ((b))(c) . We propose two methods for an independent determination of the individual children masses M-c((a)) and M-c((b)). (M) over tildep((M) over tilde ((a))(c),(M) over tilde ((b))(c)) . As we show in several examples, quite often there is a special point along that ridge which marks the true values of the children masses. Our results allow collider experiments to probe a multi-component dark matter sector directly and without any theoretical prejudice.